共查询到20条相似文献，搜索用时 15 毫秒
1.
《Journal of Atmospheric and Solar》2008,70(6):836-853
An annular eclipse occurred over Europe in the morning hours of 3 October 2005. The well-defined obscuration function of the solar radiation during the eclipse provided a good opportunity to study the ionospheric/thermospheric response to solar radiation changes. Since the peak electron density behavior of the ionospheric F2 layer follows the local balance of plasma production, loss and transport, the ionospheric plasma redistribution processes significantly affect the shape of the electron density profile. These processes are discussed here based on a comparison of vertical incidence sounding (VS) and vertical total electron content (TEC) data above-selected ionosonde stations in Europe. The equivalent slab thickness, derived with a time resolution of 10 min, provides relatively good information on the variation of the electron density profile during the eclipse. The computations reveal an increased width of the ionosphere around the maximum phase. As indicated by the available measurements over Spain, the photo production is significantly reduced during the event leading to a slower increase of the total ionization in comparison with the neighboring days. The supersonic motion of the Moon's cool shadow through the atmosphere may generate atmospheric gravity waves that propagate upward and are detectable as traveling ionospheric disturbances at ionospheric heights. High-frequency (HF) Doppler shift spectrograms were recorded during the eclipse showing a distinct disturbance along the eclipse path. Whereas the ionosonde measurements at the Ebro station/Spain in the vicinity of the eclipse path reveal the origin of the wave activity in the lower thermosphere below about 180 km altitude, the similar observations at Pruhonice/Czech Republic provide arguments to localize the origin of the abnormal waves in the middle atmosphere well below the ionospheric heights. Although ionosonde and HF Doppler measurements show enhanced wave activity, the TEC data analysis does not, which is an indication that the wave amplitudes are too small for detecting them via this interpolation method. The total ionization reduces up to about 30% during the event. A comparison with similar observations from the solar eclipse of 11 August 1999 revealed a quite different ionospheric behavior at different latitudes, a fact that needs further investigation. 相似文献
2.
Morphological analysis of variations of the critical frequency foF2 in the midlatitude ionosphere at various sectors of local time is carried out on the basis of data from ground-based stations
of vertical sounding of the ionosphere in the period when during use of the incoherent scatter radar at Saint-Santin an anomalously
strong increase in the electric field was observed at heights of the ionospheric F region in the period of enhanced geomagnetic activity (4+ < Kp < 6−). The obtained picture of the space-time distribution of disturbances in foF2 makes it possible to assume that they could be caused by penetration to middle latitudes of the large-scale electric field
of the magnetospheric convection directed westward in the nighttime and morning hours and eastward in the noon and evening
sectors. 相似文献
3.
V. V. Belikovich V. D. Vyakhirev E. E. Kalinina V. D. Tereshchenko S. M. Chernyakov V. A. Tereshchenko 《Geomagnetism and Aeronomy》2008,48(1):98-103
The results of observations of the solar eclipse ionospheric effects on March 29, 2006, are presented. The observations were conducted using the partial reflection method near Nizhni Novgorod and the vertical sounding method at the automatic ionospheric station near Murmansk. It has been obtained that the electron density at altitudes of 77 and 91 km decreases by a factor of more than 4; in this case the response of the ionosphere at an altitude of 91 km lags behind the eclipse maximum phase on the Earth by approximately 20 min. It has been established that the eclipse in the E and F1 regions of the polar ionosphere causes a change in the electron density by 15–20%. The delay time of this effect varies from 12 to 24 min depending on the altitude. It has been registered that the reflection virtual altitude at altitudes of the ionospheric F region increases in Murmansk and Nizhni Novgorod. 相似文献
4.
A. F. Yakovets G. I. Gordienko B. T. Zhumabayev Yu. G. Litvinov 《Geomagnetism and Aeronomy》2016,56(3):311-317
According to frequent five-minute vertical sounding of the ionosphere in Almaty (76°55′ E, 43°15′ N) conducted in 2000–2014, the rate of occurrence of nighttime enhancements of the electron concentration at the F2-layer maximum is analyzed, the distributions of enhancement durations are obtained, and the parameters of several very large enhancements recorded at the same time in Irkutsk and Almaty are compared. During the analyzed period, 2272 observation sessions were carried out. In 1430 sessions NmF2 enhancement was observed. The high probabilities of enhancement formation (up to 90%) in January, February, November and December are distribution features that are identical for high and low solar activity. In addition, a rapid decrease in the probability from February to March and smooth increase from September to December occurs in the same manner. High solar activity is characterized by a distinct maximum frequency in the summer months, whereas low activity is characterized by a minimum frequency. The seasonal dependence of distributions of enhancement durations is shown: durations are distributed over a wide range in the autumn–winter season and in a narrow range in the spring–summer season. 相似文献
5.
V.I. Kurkin O.M. Pirog N.M. Polekh A.V. Mikhalev I.N. Poddelsky A.E. Stepanov 《Journal of Atmospheric and Solar》2008,70(18):2346-2357
We present the results of studies of the subauroral and mid-latitude ionosphere variations in the north-eastern region of Asia. We used the data from network of vertical and oblique-incidence sounding ionosondes and optical measurements. Long-term experiments on the radio paths Magadan–Irkutsk and Norilsk–Irkutsk were carried out within the period 2005–2007. Vertical sounding stations operated in standard regime. Observation of airglow near Irkutsk was provided by the zenith photometer that measured intensities of 557.7 and 630.0 nm atomic oxygen emissions. The results may be summarized as follows. (1) Large daytime negative disturbances are observed during the main and recovery phases mainly at high latitudes, whereas the positive disturbances observed during the main phase at mid latitudes. The disturbances changed their sign between Yakutsk and Irkutsk. (2) During the main and recovery storm phases the fall of foF2 associated with the equatorward wall of the main ionospheric trough is observed in the afternoon and evening. (3) Fluctuations of the electron density more intensive at mid latitudes during the storm main phase are observed during all considered periods. They are classed as traveling ionospheric disturbances (TID). Such sharp gradients of electron density are responsible for the strong changes in the characteristics of the radio wave propagation, particularity MOF. (4) A large-scale ionospheric disturbance is noted at the meridional chain of ionosonds in December 2006 as the sharp increase of foF2. It appears in the evening in the minimum of Dst at high latitude and propagate to equator. (5) A maximum of 630 nm emission above Irkutsk corresponds to the foF2 increase. (6) The obtained experimental data on the net of vertical and oblique-incidence sounding with high time resolution show that such net is the effective facility to study the conditions of the radio wave propagation and can be used for the diagnostic of the ionosphere. 相似文献
6.
本文对1959年7月及1960年11月有关太阳貭子爆发的各种地球物理效应,作了較全面和系統的論述。文中在§2-4分別敘述了这期間地磁場扰动、极盖区电波吸收观測与电离层变动情况、以及太阳耀斑与太阳射电爆发.根据以上情况,作者特別着重在§5中論述宇宙綫强度扰乱分析（包括各国进行研究的基本情况、若干特殊分析方法与結果簡介、关于綜合观测和高空探測）,并在§6中提出了今后开展工作的几点初步意見。本文引用了北京台的磁暴与宇宙线强度变化記录,并附有較完全的文献目录。 相似文献
7.
E. V. Liperovskaya 《Geomagnetism and Aeronomy》2008,48(6):807-811
The observations of spread F during the nighttime hours (0000–0500 LT) have been statistically analyzed based on data of Tokyo, Akita, Wakkanai, and Yamagawa Japan vertical ionospheric sounding stations for the time intervals a month before and a month after an earthquake. The disturbances in the probability of spread F appearance before an earthquake are revealed against a background of the variations depending on season, solar activity cycle, geomagnetic and solar disturbances. The days with increased solar (Wolf number W > 100) and geomagnetic (ΣK > 30) activity are excluded from the analysis. The spread F effects are considered for more than a hundred earthquakes with magnitude M > 5 and epicenter depth h < 80 km at distances of R < 1000 km from epicenters to the vertical sounding station. An average decrease in the spread F occurrence probability one-two weeks before an earthquake has been revealed using the superposed epoch method (the probability was minimal approximately ten days before the event and then increased until the earthquake onset). Similar results are obtained for all four stations. The reliability of the effect has been estimated. The dependence of the detected effect on the magnitude and distance has been studied. 相似文献
8.
Tamara L. Gulyaeva 《Acta Geophysica》2007,55(2):253-266
Variations of the upper boundary of the ionosphere (UBI) are investigated based on three sources of information: (i) ionosonde-derived
parameters: critical frequency foF2, propagation factor M3000F2, and sub-peak thickness of the bottomside electron density profile; (ii) total electron content (TEC) observations from signals
of the Global Positioning System (GPS) satellites; (iii) model electron densities of the International Reference Ionosphere
(IRI*) extended towards the plasmasphere. The ionospheric slab thickness is calculated as ratio of TEC to the F2 layer peak electron
density, NmF2, representing a measure of thickness of electron density profile in the bottomside and topside ionosphere eliminating the
plasmaspheric slab thickness of GPS-TEC with the IRI* code. The ratio of slab thickness to the real thickness in the topside ionosphere is deduced making use of a similar ratio
in the bottomside ionosphere with a weight Rw. Model weight Rw is represented as a superposition of the base-functions of local time, geomagnetic latitude, solar and magnetic activity.
The time-space variations of domain of convergence of the ionosphere and plasmasphere differ from an average value of UBI
at ∼1000 km over the earth.
Analysis for quiet monthly average conditions and during the storms (September 2002, October–November 2003, November 2004)
has shown shrinking UBI altitude at daytime to 400 km. The upper ionosphere height is increased by night with an ‘ionospheric
tail’ which expands from 1000 km to more than 2000 km over the earth under quiet and disturbed space weather. These effects
are interposed on a trend of increasing UBI height with solar activity when both the critical frequency foF2 and the peak height hmF2 are growing during the solar cycle. 相似文献
9.
本文对比分析了太阳活动高、低年期间高纬日侧顶部电离层离子上行随地磁活动水平的变化特征.按地磁活动水平,将DMSP卫星在太阳活动高年（2000-2002年,F13和F15）及太阳活动低年（2007-2009年,F13;2007-2010年,F15）期间的SSIES离子漂移速度观测数据分为三组：地磁平静期（Kp<3）,中等地磁扰动期（3 ≤ Kp < 5）和强地磁活动期（Kp ≥ 5）,分别统计分析了高纬日侧顶部电离层离子上行特征的时空分布.对比分析发现：（1）太阳活动低年期间,高纬日侧电离层离子上行发生率以及上行速度峰值均是太阳活动高年的2倍多,而离子上行通量峰值只有高年的1/6-1/4;（2）在相同太阳活动条件下,地磁活动水平对日侧电离层离子上行发生率峰值的影响并不明显,但对离子上行发生率的空间分布有着显著的控制作用：电离层离子上行高发区随地磁活动向低纬度扩展,并在强地磁活动期间呈现饱和的趋势;（3）日侧顶部电离层等离子体似乎存在两个效率相当的上行区域,一个位于极尖/极隙区纬度附近,离子可沿开放磁力线上行进入磁尾;另一个位于晨侧亚极光区附近,离子沿闭合磁力线上行,有可能进入日侧等离子体层边界层. 相似文献
10.
Data from 15-minute measurements at the vertical ionospheric sounding station in Irkutsk during the summer months of 2008–2011 are analyzed in order to detect in the ionosphere effects of preparation of weak earthquakes of the K = 10–12 energy class. The method of revealing disturbances in ionospheric parameters by simultaneous observations of the sporadic E layer and regular F2 layer, which was previously applied by the authors in the case of stronger earthquakes, was used. The efficiency of using this method to detect ionospheric disturbances preceding earthquakes also in the case of weak earthquakes is demonstrated. Possible ionospheric precursors of the selected series of earthquakes are identified. For them, an empirical dependence relating the time of advance of the shock moment by the probable ionospheric precursor on the energy class of the earthquake and the epicenter distance to the observation point is found. 相似文献
11.
L. F. Chernogor 《Geomagnetism and Aeronomy》2010,50(3):346-361
Quasi-periodic variations in the Doppler shift of the HF range frequency at a vertical path and critical frequency of the
F
2 layer caused by wave disturbances in the ionosphere on the day of the partial (the magnitude was about 0.42) solar eclipse
and on background days are analyzed. For the spectral analysis, the window Fourier transform, adaptive Fourier transform,
and wavelet analysis were jointly used. It is shown that on the day of the eclipse and the background day, spectral characteristics
of wave disturbances within the 150–200 km height range differed substantially. The changes in the spectral composition began
approximately 30–35 min after the solar eclipse beginning and lasted more than 1.5 h. 相似文献
12.
The results of magnetometric observations and radar studies of the lower ionosphere during the superstrong magnetic storm (geospace storm) of November 7–10, 2004, are presented and analyzed. An increase in the electron density and in the amplitudes of its aperiodic and quasi-periodic variations at high level of magnetic activity is detected. In individual time intervals, the relation of Pc5-6 magnetic pulsations to short-period (5–15 min) wave disturbances in the electron density in the lower ionosphere was observed. 相似文献
13.
O. A. Laryunin 《Geomagnetism and Aeronomy》2018,58(2):245-251
The characteristic U-shaped traces (cusps) in ionograms are associated with the passage of traveling ionospheric disturbances (TIDs), which lead to horizontal electron density gradients in the ionosphere and, therefore, to off-angle reflections in radio sounding. A new form of representation is considered for daily ionospheric sounding data. A compound parabolic layer model is proposed, which allows analytical calculation of ray paths to speed up the “homing-in” of the rays. Changes in the shape of the trace in the ionogram due to varying the TID characteristics are examined. A discussion is given of the possibilities for estimating TID characteristics from digitized vertical sounding ionograms. 相似文献
14.
This paper presents the results of studies of wave disturbances in the electron concentration N in the ionosphere during a prominent geospace storm, in the process of which the electron concentration decreased by a factor
of 6–7, whereas the temperatures of ions and electrons at night increased up to 2000 and 3000 K, respectively. The height-time
variations in the parameters of wave disturbances are also analyzed. It is shown that the geospace storm was accompanied by
a substantial change in wave activity in the ionosphere. In the period of negative ionospheric storms, the amplitude Δ
N
decreased by a factor of 2–10. At the same time, the relative amplitude δ
N
= ΔN/N changed insignificantly and was within the limits 0.05–0.10 during day-time. At night, δ
N
reached 0.25–0.30 and sometimes even 0.4–0.5. During both disturbed and undisturbed days, quasi-periodic processes with a
period of 40–60 and 80–120 min prevailed. The maximum values of the absolute and relative amplitudes were achieved at a height
of 200–270 km. A soliton-like disturbance formed near the main phase of the magnetic storm on November 10, 2004 was detected.
Its appearance was related to the oblique coherent reflection of sounding signals. 相似文献
15.
Results of studying the ionospheric response to solar flares, obtained based on the incoherent scatter radar observations
of the GPS signals and as a result of the model simulations, are presented. The method, based on the effect of partial “shadowing”
of the atmosphere by the globe, has been used to analyze the GPS data. This method made it possible to estimate the value
of a change in the electron content in the upper ionosphere during the solar flare of July 14, 2000. It has been shown that
a flare can cause a decrease in the electron content at heights of the upper ionosphere (h > 300 km) according to the GPS data. Similar effects in the formation of a negative disturbance in the ionospheric F region
were also observed during the solar flares of May 21 and 23, 1967, at the Arecibo incoherent scatter radar. The mechanism
by which negative disturbances are formed in the upper ionosphere during solar flares has been studied based on the theoretical
model of the ionosphere-plasmasphere coupling. It has been shown that an intense ejection of O+ ions into the above located plasmasphere under the action of a sharp increase in the ion production rate and the thermal
expansion of the ionospheric plasma cause the formation of a negative disturbance in the electron concentration in the upper
ionosphere. 相似文献
16.
V. A. Ivanova V. I. Kurkin N. M. Polekh L. V. Chistyakova I. G. Brynko V. V. Chuyev Z. F. Dumbrava I. N. Poddelskii 《Geomagnetism and Aeronomy》2011,51(8):1101-1104
The morphological features of wave-like ionospheric disturbances with periods of 1–2 h and the spatial extent exceeding 1000
km are studied. Oblique-incidence sounding data of the ionosphere, obtained in eastern Siberia during several continuous monthly
experiments on three radio paths from 2006 to 2010, have been used. Large-scale traveling ionospheric disturbances generated
during magnetic storms and large-scale wave-like ionospheric disturbances registered during geomagnetically quiet periods
are considered. Small-scale ionospheric structures were also observed against a background of large-scale traveling iono-spheric
disturbances considered in this study. 相似文献
17.
The measurements of the critical frequencies of the ionospheric F2 layer based on vertical radiosounding, which was performed with a CADI digital ionosonde at the Voeykovo magnetic–ionospheric observatory in February 2013, have been considered. The observations have been compared with the upper atmosphere numerical model (UAM) data for three days that differ in the amplitude and the character of solar and magnetic activity and correspond to quiet and moderately disturbed states of the ionosphere. The work was performed in order to improve the methods for determining the ionospheric state by vertical sounding ionograms. The time variations in the F2 layer critical frequency, electric field vector zonal component, and thermospheric wind velocity meridional component have been analyzed. Calculations were performed with three UAM variants. The UAM version providing the best agreement with the CADI ionosonde data was the version in which the neutral temperature, neutral composition, and pressure gradients are calculated according to the MSIS empirical model and the horizontal neutral wind velocity is determined by the equation of motion with pressure gradients from MSIS. The calculated values corresponded to the measurements, except those for the evening, because the electron density at the ionospheric F2 layer maximum depends more strongly on electric fields and thermospheric wind velocities during this period. Thus, the indicated UAM version with the above limitations can be used to determine the state of the subauroral ionosphere. 相似文献
18.
19.
S. A. Pulinets A. D. Legen'ka T. V. Gaivoronskaya V. Kh. Depuev 《Journal of Atmospheric and Solar》2003,65(16-18):1337-1347
This paper summarizes the results of more than 10 years spent by the authors studying the variations in the ionosphere over seismically active regions several days or hours before strong earthquakes. The physical mechanisms of such variations established by the authors and published previously are submitted in the references. This article is aimed mainly at determining the major characteristic parameters of the observed effects (temporal and spatial variations, range in amplitude, etc.) to provide the means to separate the seismogenic effects from other forms of ionospheric variability. Data obtained by ground-based ionosondes and by topside vertical sounding from satellites are used in conjunction with local probe measurements. The topside vertical profiles of the electron concentration are analyzed. It is shown that the most characteristic effect is that of scale height changes in the vertical distribution of ions and electrons implying a decrease in the mean ion mass within the F-layer due to seismogenic effects. This result is supported by direct mass-spectrometer measurements. Differences between magnetic storm ionospheric disturbances and seismogenic variations within the ionosphere are also discussed. 相似文献
20.
L. F. Chernogor 《Geomagnetism and Aeronomy》2016,56(5):592-603
The results of the observations of aperiodic and quasi-periodic disturbances in E and F1 ionospheric layers and air temperature variations in the surface atmosphere on the day of the solar eclipse and control days are presented. The ionospheric processes were monitored by vertical sounding Doppler radar. The measurements showed that, near the time of the maximum coverage of the solar disk, the greatest decrease in the density of electrons in the layers E and F1 was ～27%, which is close to the calculated value (25%). The solar eclipse was accompanied by the generation of traveling ionospheric disturbances with a period of 8–12 min and a relative amplitude of electron density variations of ～0.6–1.5%. Because of the haze in the surface atmosphere, its temperature, which was monitored at observation points at a distance of 50–60 km from each other did not exceed 1°C near the time of the maximum eclipse magnitude. 相似文献